Ordinarily, vending machines utilize mechanical locks in connection with their coin boxes which obviously require mechanical keys to unlock. These types of locks are fairly expensive and, furthermore, the coin boxes secured by these locks have security limitations in that most mechanical locks are susceptible to being picked open.
Recently, electronic locks have replaced mechanical locks in many applications. These devices typically include a keypad or electromagnetic device for entry of a predetermined number sequence into a detector which only responds to the entry of the predetermined number sequence.
Automobiles have recently been made available with electronic door locks which are operated from keyboards mounted on the doors of the automobile. In an automobile, a battery is required for starting the engine; therefore, no additional power source is required to provide an electronic lock. Typically, these electronic locks are in addition to mechanical locks since the electronic locks alone are subject to failure if, for instance, the car battery is discharged to a degree where it cannot energize the locking mechanism. Such an occurrence may easily happen if the driver forgets to turn off the lights of the car.
Because electronic locks are dependent on the condition of their power sources, they are comparatively unreliable. The inability of an electronic lock to function if its power source fails has prevented electronic locks from finding applications more widespread than the securing of entrance doors in buildings or in automobiles.
In addition to the comparative unreliability of electronic locks, they are also expensive. Although the electronic components for an electronic lock are considerably cheaper than the components of a mechanical lock, the added cost of a battery brings the total cost of the electronic lock to a level comparable with the cost of a mechanical lock. The use of an a-c power outlet may reduce the cost of an electronic lock, but its reliability is sacrificed since a simple power outage makes the lock inoperable. A battery backup may be added as an emergency power source, but the additional cost of the battery reduces the attractiveness of an electronic lock as an alternative to a standard mechanical lock.
In lock applications where a battery represents an item that is otherwise not needed and also represents a significant expense in view of the total cost of the object being locked, the substitution of an electronic lock for a mechanical lock is likely not to be commercially feasible. Also, for high reliability, the electronic lock may require a mechanical lock as a backup to protect against battery failure or A-C power failure. In situations where such a backup is necessary, the electronic lock becomes merely an additional lock with its associated added expense. Therefore, electronic locks have been limited in the scope of their applications because of the foregoing practical considerations which make electronic locks, as previously available, unacceptable alternatives to mechanical locks in many environments.